Navigation

Galileo

GIOVE-A

We designed and manufactured GIOVE-A, the pathfinder satellite with a mission to secure the Galileo frequency filings at the International Telecommunications Union (ITU). GIOVE-A was designed, built and tested in a rapid 30 month programme and launched on schedule on 28th December 2005, allowing ESA to claim the frequency filings for the Galileo programme three months before the licence expired.

The satellite also played a crucial role as the test-bed for the Galileo payload units, providing a representative signal-in-space for ground-based experimentation with Galileo signals as well as characterising the radiation environment for the Medium Earth Orbit used by all future Galileo satellites.

On the 2nd May 2007 GIOVE-A successfully transmitted the first European navigation message from space, containing the information needed by users' receivers to calculate their position.

In 2012 SSTL's experimental GPS receiver on-board GIOVE-A successfully achieved a GPS position fix at 23,300km altitude - the first position fix above the GPS constellation on a civilian satellite.

GPS is routinely used via Low Earth Orbit satellites to provide the orbital position and offer a source of time to the satellite. Spacecraft in orbits higher than the 20,000km of the GPS constellation however can only receive a few of the signals that "spill over" from the far side of the Earth, meaning that the signals are much weaker and a position fix cannot always be secured.

With the support of ESA and the ARTES programme of funding, we included the SGR-GEO receiver on the GIOVE-A satellite to prove that a receiver could achieve a position fix from a higher orbit. The SGR-GEO is adapted from our SGR range of receivers and incorporates a high-gain antenna and a precise oven-controlled clock. It demonstrates special algorithms to allow reception of weak signals and an orbit estimator intended to allow a near continuous position fix throughout orbit.

Galileo Navigation Payloads

We have designed, manufactured and supplied 22 navigation payloads for the deployment phase of Europe's satellite-supported navigation system, Galileo, and we are now manufacturing a further 12 payloads for delivery to our partners, OHB-System in Germany. Our payload solution is based on European sourced atomic clocks, signal generators, high power TWTAs and Antennas.

GNSS Receivers, Antennas and Instruments

Our Space GNSS receivers (SGRs) are highly regarded for quality and robustness and are flying on many missions, including NASA's CYGNSS constellation which measures the winds within cyclones, hurricanes and typhoons.

Space GNSS Receivers (SGRs) routinely provide position, velocity and time information to satellites in low Earth orbit, and more than 70 orbiting satellites have used receivers and antennas provided by SSTL, on missions from UKSA, ESA, NASA, USAF, JAXA and on the International Space Station. SSTL’s receivers are based on COTS components, with radiation mitigation and quality processes to suit small satellite applications. The oldest operational mission continues to use our SGR-10 receiver after 17 years in orbit. SSTL provides receivers and antennas in formats to suit different applications, including Cubesat, OEM and boxed configurations.

SSTL demonstrated the re-use of GNSS signals reflected off the ocean like radar transmissions to enable measurement of geophysical parameters, such as ocean wind, ice extent and soil moisture. The SGR-ReSI (Remote Sensing Instrument) is operating in orbit on TechDemoSat-1 and measurements are available via the website www.merrbys.org.

SSTL’s SGR-ReSI was selected for the NASA CYGNSS mission, and has been flying on the 8 small CYGNSS satellites since 2016. As a result of this work, GNSS-Reflectometry is quickly establishing itself as a new low cost way of observing the Earth.